WO2007101658A1

WO2007101658A1 - Method for recording input signal variations

Info

Publication number: WO2007101658A1
Application number: PCT/EP2007/001931
Authority: WO
Inventors: Detlef Arndt; Rolf Horstmann
Original assignee: Pepperl + Fuchs Gmbh
Priority date: 2006-03-08
Filing date: 2007-03-06
Publication date: 2007-09-13
Also published as: DE102006010748A1

Abstract

The invention relates to a method for recording input signal variations, especially of field appliances used in potentially explosive regions, said variations occurring at an inlet of at least one input/output device. Said device is connected to a communication unit by means of a local connection line, the communication unit being in turn connected to an automation system by means of an external connection line. One such automation system is a programmable process control system, a stored-program control system or a personal computer. In order to be able to establish, in a simple manner, the time at which one such input signal variation or a sequence of input signal variations occurs, a time mark is associated with each input signal variation. The input signal variation and associated time mark are then stored as call data especially in the communication unit. The call data is called up cyclically or at pre-determined times by the automation system via the external connection line.

Description

Method for recording input signal changes

The invention relates to a method for recording input signal changes at an input of at least one input / output unit, in particular for connection to field devices located in the potentially explosive area (Ex area), which input / output unit is connected to a communication unit via a local connection line. This in turn is connected by means of an external connection line with an automation system. Such an automation system may be a programmable process control system, a programmable logic controller or even a personal computer or the like.

With such an automation system can be connected via the corresponding external connection line, a plurality of communication units, each of which is connected via the corresponding local connection line with a series of input / output units. Each of these input / output units can be connected to one or more field devices. In this case, there is also the possibility that input signals are transmitted in a multi-channel form by a field device, wherein, in particular, data can also be exchanged between input / output unit and associated or assigned field device or field devices.

Although there is already the possibility of data exchange in known units connected to such automation systems. Such a data exchange between, in particular, field device and automation system can serve to transmit a corresponding error message from the field device to the automation system. However, it has hitherto not been possible to associate a particular time with an input signal change indicative of an error at the input of a corresponding input / output unit, or even to establish an order of occurrence of such input signal changes from different field devices.

The invention is therefore based on the object to improve a method of the type mentioned in such a way that the above shortcomings at the same time maintaining all other advantages of the corresponding compounds and in particular for hazardous areas are eliminated.

This object is achieved by the features of claim 1.

According to the invention, an assignment of a time mark to each input signal change takes place first. As a result, a point in time (time stamp) of the occurrence of the input signal change is determined at least in a corresponding branch of the communication unit and assigned input / output units and field devices. Subsequently, the Eiπgangssignaländerungen are stored with the associated time stamp as retrieval data. This is done in particular in the communication unit, but can also be done locally for this branch elsewhere, such as in each corresponding input / output unit.

Finally, there is still a retrieval of the retrieval data via the first connection line, which is usually done by the appropriate automation system.

As a result, it is possible according to the invention not only to perform an accurate time specification of the input signal changes, but also to determine the sequential occurrence of such input signal changes on the basis of the temporal determination of the corresponding input signal changes. The types of input signal changes or the information corresponding thereto can be defined in a known manner.

Examples of such input signal changes is a change of a binary input signal or a state change or the like. Such a state change can be, for example, a line fault or even a short circuit.

The corresponding input signal changes may correspond to status and / or error messages, which are then detected and monitored in real time.

With regard to the corresponding field devices, it should also be noted that these actuators or sensors can be. Actuators receive corresponding data from the automation system. They actively act on a corresponding process, while sensors detect states and data that occur during the process and transmit this information to the automation system. In both cases, the communication between the automation system and the field device can be bidirectional.

The retrieval of the retrieval data can be done acyclically and / or sequentially. Such acyclic retrieval is also possible for control, diagnostics, parameterization, alarm function or upload and download.

The connection between the automation system and field devices via a bus plan, backplane rail, Profibus or the like as a local connection line.

A corresponding bus plan or backplane rail can also be arranged in a control cabinet. Corresponding input / output units can be detachably arranged as modules on the corresponding rail or backplane. The communication unit with, if appropriate, further units such as the power supply unit, the bus coupling unit, the output separation unit, the transmitter power supply unit or the like can likewise be arranged on this rail. In an analogous manner, the connection with a Profibus, a Modbus or the like can be done as a fieldbus communication connection.

In this connection, the corresponding external connection line can be used to fetch the corresponding input signal changes and of course also to communicate and control the corresponding unit via a fieldbus with a fieldbus protocol such as Profibus, Modbus or the like, optical fibers, Ethernet or the like. As described above, this fieldbus also transmits corresponding input and output data between the field device and the automation system. Other functions can be supported, such as configuring the field device, reading the configuration of the field device, parameterizing the units, reading alarms and diagnostics data of the field devices, etc.

It has already been pointed out briefly that the communication unit can detect the input signal changes in real time. There is also the possibility that each communication unit communicates with a number of input / output units, with each of these input / output units being assigned at least one field device

In order to be able to store the corresponding input signal changes for all connected emitter and output units as well as associated field devices with a corresponding assignment, the assigned communication unit can have a memory device for storing these input signal changes

Furthermore, a master unit as a central control unit of the automation system can transmit a common time base to at least all connected communication units and / or input / output units. This common time base essentially results in an absolute time measurement for all occurring input signal changes and no, for example, any communication input. In this way, it is possible to determine the exact time occurrence and the chronological sequence of corresponding input signal changes for the overall system

In order to transmit the time base of all connected units from the master unit, there is a first possibility for simultaneous transmission or else a second possibility for the sequential transmission of the corresponding time base

In both cases, it may turn out to be advantageous if, after transmission of the time base, a synchronization signal is transmitted

To respond quickly to the transmission of the appropriate time base for timing, an interrupt can be used

In order to continue to ensure after a certain time that a common and synchronous time base is used, the corresponding time setting can be repeated at predetermined tent intervals, in particular to compensate for vibration deviations of a quartz. A calculation of such a deviation may be due to standard deviations from data sheets of the corresponding clock or the quartz.

In order to enable intrinsically safe operation of the communication units as well as the further units connected thereto, the corresponding communication unit can be assigned a bus coupling unit which intrinsically reliably couples the external connection line with the communication unit or directly with the group of input / output units.

In general, it is also advantageous if each field device can be exactly identified by the automation system, which can be done for example by assigning a unique address to the input / output unit or directly to the field device connected to this.

The corresponding address can be stored together with input signal change and timestamp as polling data.

It has already been pointed out above that the master unit can cyclically exchange data with the field devices, whereby this also takes place via the corresponding communication unit and the assigned input / output units.

According to the invention, another advantage is that the sampling rate or time for an input signal change is relatively low and less than 10 ms, with a maximum value for an accuracy of the occurrence of an input signal change from the sum of internal cycle time and sampling time of the Kσmmunikationsein- unit and Accuracy of the corresponding timer.

In the following, an advantageous embodiment of the invention will be explained in more detail with reference to the accompanying figures in the drawing.

Show it: 1 is a schematic representation of an automation system with connected subunits such as communication units, input / output units and field devices, and

Fig. 2 timing diagram for illustrating the ^" occurrence of an input signal change and their detection.

1 shows a schematic diagram for an automation system 6 with communication units 4 connected via an external connection line 5. These are connected via a local connection line 3 to corresponding input / output units 2. Each of these input / output units 2 has one or more inputs / outputs 1, wherein respective field devices 11 in the form of actuators or sensors with one or more of these inputs / outputs 1 are connected.

The field devices 11 are arranged in particular in explosion-proof areas. Corresponding actuators or sensors may be actuators, regulators, valves, switches, temperature sensors or the like.

The local connection line 3 can be designed as a bus plan, backplane rail, fieldbus with a corresponding protocol or the like. In particular, in the case of implementation as a bus plan or backplane rail, corresponding input and output units and the communication units can be arranged in a control cabinet and all modules can be detachably fastened to the bus plan or backplane rail. Other units can also be attached there.

The communication unit 4 has a memory device 8, for example in the form of a ring memory and serves to store input signal changes to inputs 1 of the corresponding input / output units 2. These input signal changes can be changes of binary input signals or state changes such as line fault or short circuit. All corresponding data is collected in the memory device 8. Each input signal change is assigned a time stamp in order to be able to determine the time occurrence of the change and also the temporal sequence different input signal changes at different times.

The input state changes and associated time marks stored in the memory device 8 are acyclically and sequentially readable via the external connection line 5.

The external connection line 5 is a field bus, an optical waveguide, an Ethemet connection or the like, the field bus 7 having a protocol such as Profibus, a Mod ^* bus or the like.

For intrinsically safe training, each of the communication units 4 is assigned to a bus coupling unit 10. This bus coupling unit 10 can also be part of the communication unit 4 corresponding to the memory device 8.

In addition to the transmission of such input signal changes, a data exchange between, for example, a master unit 9 of the automation system 6 and the subordinate units, such as communication unit 4, bus coupling unit 10, memory device 8, input / output unit 2, and field devices 11 takes place via the corresponding connection lines.

It should be noted in general that only a portion of an overall system is shown in Fig. 1, wherein for simplicity only a few field devices and only a small number of communication units is shown.

The operation of the system shown in FIG. 1 will be briefly described below.

If corresponding input signals of the input / output units 2, which are transmitted by corresponding field devices 11, are assigned, a time stamp is assigned to this input signal change and a storage of both in the memory device 8. The corresponding input signal change takes place in real time by the input / output unit with a corresponding time measurement error is less than 1.5 ms. The input / output unit can also be a multi-channel unit which is not only connected to a field device or which is connected to a field device via a plurality of inputs. The appearance of the input signal change is transmitted via the local connection line 3 to the communication unit 4 and stored there with an associated time stamp in the memory device 8. From this memory device, the corresponding data can be read out acyclically and sequentially by the master unit 9 of the automation system 6.

Such an automation system may be a programmable control system, a programmable logic controller or even a personal computer, in particular for process automation.

In order to be able to use the time mark assigned to each input signal change as the absolute time mark, the transmission of a common time base takes place from the master unit 9 or the automation system 6 to all connected units. The corresponding time base can be transmitted simultaneously to all or at least some of the connected units.

The transmission of the corresponding time base is usually carried out sequentially to the subordinate units and then there is a synchronization. A start of the time measurement can take place at the same time by an interrupt in all subordinate units.

The determination of the common time base may be repeated at certain intervals to eliminate timing inaccuracies in the various units. It has been found that the inaccuracy of the common time base is less than 10 ms, which time essentially results from the internal cycle time of the input / output unit and the sampling time of the communication unit and the accuracy of the corresponding timer or clock.

FIG. 2 shows a corresponding time diagram for determining an input signal change and the error associated with this determination. On the vertical axis is the corresponding event, ie the input signal change is shown, see Φ. The horizontal axis shows the time in ms.

The corresponding occurrence of the event is shown in the top graph and directly below it is shown the corresponding storage of the input signal change or the event in the communication unit 4 at ©. The storage takes place after a maximum of one cycle time T _C γc of the communication unit, see the third graph from above in FIG. 2.

After a delay time of T _DLY , diagnostic information can be provided and after a corresponding polling time T _PLC the automation system queries the corresponding memory device of the communication unit 4. This polling time depends on the number of subunits, the transmission rate and service routines of the master unit ,

The corresponding query is made at ©.

After the corresponding diagnostic information has been conventioned, see the fourth graph from the top in FIG. 2, a reset occurs at ©.

Furthermore, an update time Tu _Pd in the uppermost graph in FIG. 2 is indicated, which relates to an update of the occurrence of the input signal changes, wherein corresponding events are read in again by the communication unit after the update time, whereby these operate with time division multiplexing can.

According to the cycle time of the communication unit is also a storage, see time interval Tstack-

It should also be pointed out that the automation system 6 or the master unit 9 provides a common time base for all units connected via the external connection line 5. The corresponding time information is transmitted simultaneously to all or at least some of the units. This is done in usually in two steps. In a first step, the time base is transmitted sequentially to the selected units. Thereafter, a synchronization signal for setting the corresponding clocks at each unit is transmitted to the units for starting a corresponding clock for timing. Upon receipt of the corresponding time base, an interrupt for setting the time occurs simultaneously at all corresponding units. The adjustment of the time may be repeated at predetermined time intervals depending on the accuracy of the respective clock.

The timing depends on the accuracy of the clock and also the duration of the interrupt routine. In addition, the sampling rate of the particular multi-channel input / output unit must be considered. Overall, this results in an estimate for a time error of less than 10 ms, this time error resulting from the internal cycle time of the communication unit, the sampling time of the input / output module and the corresponding accuracy of the clock.

Thus, according to the invention, a time synchronization in an automation system with connected units is possible in a simple manner, as is a recording of corresponding input signal changes of input / output units, to each of which a timestamp is assigned and which together with this timestamp can be transmitted to a corresponding automation system.

Claims

claims

1. A method for recording input signal changes, in particular arranged in the hazardous area field devices, at an input (1) at least one input / output device (2) which is connected via a local connection line (3) with a communication unit (4) by means of an external connection line (5) to an automation system (6), such as process control system (PLS), programmable logic controller (PLC) or personal computer (PC),

marked by

the steps:

a) assigning a timestamp to each input signal change; b) storing input signal change and associated time stamp as retrieval data, in particular in the communication unit (4), and c) retrieving the retrieval data from the automation system (6) via the external connection line (5)

2. The method according to claim 1, characterized in that the input signal change is a change of a binary input signal, a state change, such as line fault or short circuit, or the like.

3. The method according Anspruchi or 2, characterized in that the retrieval of the retrieval data is acyclic and / or sequential.

4. The method according to any one of the preceding claims, characterized in that the connection via a bus plane, backplane rail, Profibus or the like as local connection line (3).

5. The method according to any one of the preceding claims, characterized in that the retrieval of the retrieval data via a fieldbus with a fieldbus protocol such Profibus, Modbus or the like, optical fiber, Ethernet or the like as an external connection line.

6. The method according to any one of the preceding claims, characterized in that the communication unit (4) detects the input signal change in real time.

7. The method according to any one of the preceding claims, characterized in that the communication unit (4) with a number of input / output units (2) is in communication.

8. The method according to any one of the preceding claims, characterized in that the communication unit (4) stores the input signal change and associated time mark in a memory device (8).

9. The method according to any one of the preceding claims, characterized in that a central master unit (9) of the automation system (6) transmits a common time base to at least aiie connected communication units (4) and / or input / output units (2).

10. The method according to claim 9, characterized in that the time base is transmitted simultaneously to all connected units (2, 4) of the master unit (9).

11. The method according to claim 9 or 10, characterized in that the time base to the connected units (2, 4) from the master unit (9) is transmitted sequentially.

12. The method according to any one of the preceding claims 9 to 11, characterized in that after transmission of the time base of the master unit (9), a synchronization signal is transmitted.

13. The method according to any one of the preceding claims, characterized in that a time adjustment of all with the Mastereiπheit (9) connected units (2, 4) takes place by means of the time base by an interrupt.

14. The method according to claim 13, characterized in that the Zeiteinstelluπg is repeated at predetermined time intervals, in particular to compensate for vibration deviations of a quartz.

15. The method according to any one of the preceding claims, characterized in that one of the communication unit (4) associated bus coupling unit (10) the intrinsic safety coupled to the external connection line (5) in particular with a group of input / output units (2) and connected field devices.

16. The method according to any one of the preceding claims, characterized in that each input / output unit or associated field device (11) is assigned a unique address.

17. The method according to any one of the preceding claims, characterized in that the master unit (9) acyclically with the field devices (11) exchanges data.

18. The method according to any one of the preceding claims, characterized in that a sampling rate or time for each input signal change results in a maximum of the sum of internal cycle time of the communication unit (4), sampling time of the input / output unit and accuracy of a corresponding timer (12) ,